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The Proper "Balboni" Rear-Wheel Drive RWD Conversion for Gen 1 R8
I've been thinking about converting my Gen 1 V10 to RWD, but have read posts here outlining how the suspension is not properly setup for RWD and that there would be performance issues.
There were no Gen 1 RWD R8s, but there was a RWD version on the same platform: the 2010 Lamborghini Gallardo LP550-2 Valentino Balboni. The was and is considered to be the ultimate version of the Gallardo, designed to specifications of their chief test driver of 40 years. This seems like the reference setup required for a "factory approved" RWD setup. I did some research and here's what I think is required to implement the Gallardo Balboni RWD setup.
Reasons why you should do a RWD conversion:
Below is what I believe needs to be changed to do the RWD conversion.
1. Remove the Front Wheel Drive Components: Here's the parts list and expected weight savings.
2. New Anti-Roll Bars Front and Rear: +30% front / -30% rear of 4wd bars torsional stiffness. The Balboni uses a re-configured sway bar setup to make the front more stiff and the rear less stiff.
3. Suspension - Spring Rates, Alignment, Ride Height: Since the static load distribution of the car has changed slightly, the springs rates need to be adjusted. To correctly lower and compensate, the rear spring needs to be slight firmer than stock. The front likely needs to be slightly softer than stock. I'm working to figure out what this may be and looking for suggestions.
4. (Optional) Upgrade the Rear Limited Slip Differential: The Gallardo Balboni 550-2 has a taller final drive ratio vs. prior Gallardos. All Gen 1 R8 V10s and all Gen 1 Facelift V8s already came with this taller final drive ratio, so there is no change needed to the rear LSD. However, it could be worthwhile to upgrade to a helical-style LSD.
This is what I've been able to put together so far. What do you think?
There were no Gen 1 RWD R8s, but there was a RWD version on the same platform: the 2010 Lamborghini Gallardo LP550-2 Valentino Balboni. The was and is considered to be the ultimate version of the Gallardo, designed to specifications of their chief test driver of 40 years. This seems like the reference setup required for a "factory approved" RWD setup. I did some research and here's what I think is required to implement the Gallardo Balboni RWD setup.
Reasons why you should do a RWD conversion:
- RWD is ultimate driver's version of the platform, according to legendary Lamborghini test driver Valentino Balboni.
- Better steering feel due to the front wheels not being driven
- No tire/differential scrubbing sounds during tight low-speed turns
- More fun RWD driving dynamics
- Faster acceleration due to lower vehicle weight and eliminated rotational power loses from the front wheel drive system (but only as long as the rear tires get full traction, which isn't usually an issue)
- Slightly better clutch life due to reduced clutch lock-up forces
- Fully reversible back to AWD
- It's faster on the track. Ok, well, maybe not. But if the suspension is properly setup, it should be very, very close to the AWD.
Below is what I believe needs to be changed to do the RWD conversion.
1. Remove the Front Wheel Drive Components: Here's the parts list and expected weight savings.
- Remove Front Diff: 50 lbs
- Remove Drive shaft: 18 lbs
- Remove Front axles: 9 lbs each
- Add axle delete caps with tone wheels: 1.5 lbs each ($600)
- Net weight reduction: ~83 pounds
2. New Anti-Roll Bars Front and Rear: +30% front / -30% rear of 4wd bars torsional stiffness. The Balboni uses a re-configured sway bar setup to make the front more stiff and the rear less stiff.
- Balboni Front Anti-Roll Bar: 31mm, Part Number: 400411309F ~$275 (stock 4WD version weighs 8.6 pounds, thicker-walled Balboni version weighs 10.6 pounds) + 2x bushings 4D0411327J
- Balboni Rear Anti-Roll Bar: 22mm, Part Number: 400511409J ~$405 (stock 4WD is 24mm) + 2x bushings (I think it’s bushing 4D0411327J not bushing 4D0411327G)
- Torsional stiffness of the bar is ^4, so this is a significant change with 70% rear stiffness and 130% front stiffness going from 4wd to the 2wd .
- Use the Balboni stubs or machine FEBI Audi A8 stubs to the required dimension
- The rear bumper and muffler must be removed to change the rear anti-roll bar
3. Suspension - Spring Rates, Alignment, Ride Height: Since the static load distribution of the car has changed slightly, the springs rates need to be adjusted. To correctly lower and compensate, the rear spring needs to be slight firmer than stock. The front likely needs to be slightly softer than stock. I'm working to figure out what this may be and looking for suggestions.
- Ride Height: Due to the removed weight in the front an middle of the car, the front will need to be lowered 2-4 mm to get back to the stock ride height and the rear will need to be lowered 1-2 mm to get back to stock ride height. These are not substantial changes and can probably be ignored if necessary.
- Spring Rates:
- Stock Front Stock Spring Rate (R8 GT): TBD
- Stock Rear Stock Spring Rate (R8 GT): TBD
- New Front Stock Spring Rate (RWD): TBD
- New Rear Stock Spring Rate (RWD): TBD
- Alignment Specs (thanks extrablack):
- Stock Front: Camber -0 degrees 50' to -1 degrees 10', Left/Right Toe 0 degrees 06' to 0 degrees 14', total Toe 0 degrees 12' to 0 degrees 28', Total Steer Ahead -0 degrees 03' to 0 degrees 03'
- Stock Rear: Camber -0 degrees 45' to -1 degrees 15', Left/Right Toe 0 degree 05' to 0 degrees 15', Total Toe 0 degrees 10' to 0 degrees 30'
- New Front: Camber -1 degree (same), Left/Right Toe 0 degree 15', total Toe 0 degrees 30', Total Steer Ahead 0.0 degrees (same)
- New Rear: Camber -1 degree 46', Left/Right Toe 0 degree 18 ', Total Toe 0 degrees 36'
4. (Optional) Upgrade the Rear Limited Slip Differential: The Gallardo Balboni 550-2 has a taller final drive ratio vs. prior Gallardos. All Gen 1 R8 V10s and all Gen 1 Facelift V8s already came with this taller final drive ratio, so there is no change needed to the rear LSD. However, it could be worthwhile to upgrade to a helical-style LSD.
- Wevetrac helical-style limited slip differential. Part number 35-309-150WK. $1335 from XLR8 Performance
- The Wavetrac design doesn't wear out (unlike the stock differential) and, if a wheel loses traction, this design biases torque to the planted wheel instead of the unloaded wheel.
This is what I've been able to put together so far. What do you think?
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I would suggest running your plans past Ricky @ REP as he has done a few himself.
Do it and don’t look back!
You won’t find any answers easily on the spring rates. I’ve talked to Scott and directly with Audi and Bilstein about getting the rates, and no one will give it up. Proprietary information that Audi owns. I’m on Bilstein Clubsports.
I went RWD and used the Gen 2 carbon front sway with adjustable end links. **Not bolt in
The weight is slightly off from what you posted as to what actually came off of mine. I was a smidge over 86 pounds in full. The Carbon bar weighs the same as the stock front.
I’ve never thought about changing the diff. I’ve never experienced any and would not be sure what the benefits, or the deficiencies of the stock.
You won’t find any answers easily on the spring rates. I’ve talked to Scott and directly with Audi and Bilstein about getting the rates, and no one will give it up. Proprietary information that Audi owns. I’m on Bilstein Clubsports.
I went RWD and used the Gen 2 carbon front sway with adjustable end links. **Not bolt in
The weight is slightly off from what you posted as to what actually came off of mine. I was a smidge over 86 pounds in full. The Carbon bar weighs the same as the stock front.
I’ve never thought about changing the diff. I’ve never experienced any and would not be sure what the benefits, or the deficiencies of the stock.
I have a RWD V8 conversion. I’ve heard the front sway bar doesn’t need to be replaced, it’s already the same as the balboni gallardo.
I have the balboni rear sway bar and stubs but haven’t gotten around to replacing it.
I’ve never heard about #4.
in addition, I changed the toe and camber settings to match the Balboni Gallardo alignment specs.
I have the balboni rear sway bar and stubs but haven’t gotten around to replacing it.
I’ve never heard about #4.
in addition, I changed the toe and camber settings to match the Balboni Gallardo alignment specs.
I just talked to @TriniTT and we’re pretty certain there is a difference. The diameter appears to be the same as an R8 but the Balboni version weighs 4 pounds more, so presumably it has a thicker wall.I’ve heard the front sway bar doesn’t need to be replaced, it’s already the same as the balboni gallardo.
Do you have the part munber for the stubs?I have the balboni rear sway bar and stubs but haven’t gotten around to replacing it.
Do you have those specs?in addition, I changed the toe and camber settings to match the Balboni Gallardo alignment specs.
Following with great interest!
If you do a detailed comparison I’d be interested in seeing if there is a difference but I think even the part number of the bars were exactly the same.I just talked to @TriniTT and we’re pretty certain there is a difference. The diameter appears to be the same as an R8 but the Balboni version weighs 4 pounds more, so presumably it has a thicker wall.
I don’t have the part number for rear stubs but I bought them from the same place I bought the rear sway bar.
here are my current RWD alignment specs
One reason I haven’t updated suspension to something like Ohlins yet is because there’s not a lot of good information for how to get them dialed in right for a RWD gen 1 conversion. Load distribution is somewhat different and even more if you use a lightweight 8 pound battery, might have to do corner weighting of the car to get some precise numbers.
I updated the original post with these details.here are my current RWD alignment specs
Another thing I’ve been wondering about is if you go RWD would there be a benefit to a staggered wheel setup with maybe an inch difference from from front to rear wheel.
On my Evo RWD I’m planning to do 20/21 inch wheels and I’m wondering if maybe I should do 19/20 on the R8.
On my Evo RWD I’m planning to do 20/21 inch wheels and I’m wondering if maybe I should do 19/20 on the R8.
I don't think there would be much of a performace improvement, but it would definitely be a good, aggressive look. It would theoretically shift the weight forward a bit, without creating a bigger gap between the tire and fender. But the increased wheel weight and the higher effective gear ratio from the larger tire diameter would likely be negatives. But I don't think this conversion is all about absolute performance anyway - it's about what makes the car more fun to drive, and the staggered wheels would add a nice aggressive look.Another thing I’ve been wondering about is if you go RWD would there be a benefit to a staggered wheel setup with maybe an inch difference from from front to rear wheel.
On my Evo RWD I’m planning to do 20/21 inch wheels and I’m wondering if maybe I should do 19/20 on the R8.
Hi
I built on RWD in 2014 and only used the rear Balboni torsion bar. (the first conversion worldwide)
My suspension is H&R Monotube and the R8 rides perfectly.
The tires are Michelin PS2 N2 with Porsche marking and are perfect for rear-wheel drive.
Tom
I built on RWD in 2014 and only used the rear Balboni torsion bar. (the first conversion worldwide)
My suspension is H&R Monotube and the R8 rides perfectly.
The tires are Michelin PS2 N2 with Porsche marking and are perfect for rear-wheel drive.
Tom
Is downforce at the front impacted significantly from taking all those pounds off? Rake angle needs adjustment?
Aerodynamic down force is unchanged so long as the front suspension is lowered back down a few mm. But it shouldn’t be that different regardless.Is downforce at the front impacted significantly from taking all those pounds off? Rake angle needs adjustment?
Physically, there will less weight on the front wheels, but there is also less mass changing direction when turning. The ratio of downward force to lateral frictional force retains the same portion, so the weight change is a wash from a tire friction perspective.
86lbs is what is removed, but the front axle stubs you put in add back 3lbs total.The weight is slightly off from what you posted as to what actually came off of mine. I was a smidge over 86 pounds in full.
2.2lbsI just talked to @TriniTT and we’re pretty certain there is a difference. The diameter appears to be the same as an R8 but the Balboni version weighs 4 pounds more, so presumably it has a thicker wall.
10.8lbs is the balboni bar weight
8.6lbs is the stock bar weight
They are definitely different
Thanks for the info Tom! I’ll add this to the original post.
PN: 086525021H
DIFFERENTIAL (2WD - 55/65) $5,091.52
After looking through the specs of the differential, I’m pretty sure the only difference with the Balboni is the taller input gear ratio. The Audi R8 V 10 is already using the taller ratio, so there’s no change the differential required, unless you want the performance and durability upgrade of the Wavetrac. The first post has been updated accordingly.
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